feat(ui): 优化组件样式并添加现代弹窗模板

- 更新 trade_button.dart 使用新颜色系统
- 更新 coin_card.dart 使用新颜色系统
- 更新 asset_card.dart 使用新颜色系统
- 创建 modern_dialog.dart 现代弹窗模板
- 创建 modern_bottom_sheet.dart 现代底部抽屉模板

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

flutter_monisuo/lib/ui/components/coin_card.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:shadcn_ui/shadcn_ui.dart';
-import '../../core/constants/app_colors.dart';
+import '../../core/theme/app_color_scheme.dart';
 
 /// 币种卡片组件 - 用于显示币种信息
 class CoinCard extends StatelessWidget {
@@ -38,7 +38,7 @@ class CoinCard extends StatelessWidget {
               width: 44,
               height: 44,
               decoration: BoxDecoration(
-                color: theme.colorScheme.primary.withOpacity(0.1),
+                color: theme.colorScheme.primary.withValues(alpha: 0.1),
                 shape: BoxShape.circle,
               ),
               child: Center(
@@ -75,13 +75,13 @@ class CoinCard extends StatelessWidget {
             Container(
               padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 6),
               decoration: BoxDecoration(
-                color: AppColors.getChangeBackgroundColor(isUp),
+                color: getChangeBackgroundColor(isUp),
                 borderRadius: BorderRadius.circular(6),
               ),
               child: Text(
                 change,
                 style: TextStyle(
-                  color: AppColors.getChangeColor(isUp),
+                  color: getChangeColor(isUp),
                   fontWeight: FontWeight.w600,
                 ),
               ),